Compact fluorescent lamp, self-ballasted fluorescent lamp and luminaire

ABSTRACT

A compact self-ballasted fluorescent lamp which is equivalent to a typical light bulb is provided. The self-ballasted fluorescent lamp includes a cover, a lighting circuit, an arc tube-a base and a globe and formed into a shape whose outline dimensions are nearly identical to the standard dimensions of a typical light bulb. The arc tube is comprised of a plurality of U-shaped bent bulbs which have an inner tube diameter ranging from 6 to 9 mm and arranged in parallel with one another. Having a bulb height ranging from 50 to 60 mm and a discharge path from 200 to 300 mm long, the arc tube is designed such that the total luminous flux is not less than 700 lm with a lamp efficiency of not less than 60 lm/W when the lamp is lit at the lamp power of 7 to 15 W. An envelope comprising the cover and the globe has a height ranging from 110 to 125 mm, including the height of the base.

This patent application claims the benefit of priority, under 35 U.S.C.§120, as a continuation application of U.S. patent application Ser. No.09/996,314, filed Nov. 28, 2001 now U.S. Pat. No. 6,781,315, issued Aug.24, 2004 which is a divisional of U.S. patent application Ser. No.09/242,227, filed Feb. 11, 1999, which is a U.S. National Stage ofInternational Application No. PCT/JP98/02556, filed Jun. 10, 1998 nowU.S. Pat. No. 6,437,502, issued Aug. 20, 2002, hereby incorporatedherein by reference, in its entirety.

TECHNICAL FIELD

The present invention relates to a compact fluorescent lamp and aself-ballasted fluorescent lamp which are made to an even smaller scale,and also relates to a luminaire.

BACKGROUND ART

Examples of conventionally known self-ballasted fluorescent lampsinclude a self-ballasted fluorescent lamp which is provided with acover, a lighting circuit contained in the cover, and an arc tube bentor otherwise formed into an appropriate shape and contained in a globe,said cover having a base that can be mounted in a socket designed for atypical light bulb.

A self-ballasted fluorescent lamp commercially available at presenttypically has such specifications as a height of approximately 130 mm(including the height of the base), an outer diameter of approximately70 mm, an outer tube diameter of the arc tube of approximately 12 mm, adischarge path length of approximately 280 mm, a tube wall thickness ofnot less than 1.1 mm, and a lamp power of approximately 13 W. Due to itsconfiguration, however, it is difficult to provide a fluorescent lampwhich has such an arc tube and is as compact as typical light bulb.Nevertheless, there is an increasing demand for fluorescent lamps madeto an even smaller scale.

Another example of self-ballasted fluorescent lamps is disclosed inJapanese Patent Laid-open No. 1987-12051, which relates to a fluorescentlamp, wherein an arc tube having three U-shaped bent bulbs is disposedin such a way that the three U-shaped bent bulbs respectively correspondto the three sides of an approximately equilateral triangle. However, asthere is no detailed discussion in the above Japanese Patent PublicDisclosure as to various criteria regarding the reduction of thedimensions of the lamp, such as dimensions and the shape of the arc tubeas well as criteria for lighting the lamp, the invention disclosed insaid publication does not provide the optimum configuration for reducingthe dimensions of the lamp.

Another example of fluorescent lamps is disclosed in Japanese PatentLaid-open No. 1987-12051, wherein the arc tube of the fluorescent lampis formed in a U-like shape having corners bent at approximately 90°.However, the configuration having such an arc tube, i.e. an arc tubehaving sharp corners, presents a problem of irregularity in luminance,because the corners of the arc tube are too close to the globe when thearc tube is contained in the globe which is as small as that of atypical light bulb.

Another example of fluorescent lamps is disclosed in Japanese PatentLaid-open No. 1997-69309, wherein the arc tube is bent into a spiral orother shape so as to produce a lamp having a shape and dimensions nearlyidentical to those of a typical light bulb. However, a configurationwhich calls for bending the arc tube into such a complicated shape as aspiral requires a complicated production process and presents a problemin that reduction of production costs is difficult. As it is difficultto put such an arc tube in practical use for reasons described above, anarc tube having U-shaped bent bulbs is normally used. However, a lamphaving such an arc tube, too, is difficult to be made compact, becauseit imposes various limitations in the shape and the dimensions of theU-shaped bent bulbs.

When the dimensions of a fluorescent lamp are reduced, there arises thedanger of heat from the arc tube exerting an unfavorable influence onthe lighting circuit that is contained in the cover. As a fluorescentlamp disclosed in Japanese Patent Laid-open No. 1996-273615, one of theknown ways to solve this problem is a configuration which calls fordisposing a circuit board for mounting components of the lightingcircuit thereon in such a manner that the components are positionedapart from the ends of the arc tube at which the electrodes areprovided. As a result of the reduction of the dimensions of fluorescentlamps, however, circuit boards, too, are made compact. Therefore, theabove configuration presents a problem in that the reduction in thespace in which the necessary components are mounted increases the planardimensions of the lamp too much, particularly at the part where thecover is located.

Regarding a self-ballasted fluorescent lamp which is provided with acover having a base that can be mounted in a socket designed for anincandescent lamp, a lighting circuit contained in the cover, and an arctube bent or otherwise formed into an appropriate shape and contained ina globe, a configuration which calls for disposing a circuit board atthe base-facing end of an arc tube that is bent in a U-like shape andarranging electrical components on both end of the circuit board iswidely known. One of examples of such configuration is disclosed inJapanese Patent Laid-open No. 1988-245803. Compared with theaforementioned configuration which calls for positioning the circuitboard apart from the ends of the arc tube, said configuration disclosedin Japanese Patent Laid-open No. 1988-245803 is more effective inreducing the horizontal dimensions of the lamp at the region of thecover. On the other hand, it presents such problems that interferencebetween the electrical components and the arc tube, especially betweenthe electrical components and the end of the arc tube, increase theinfluence of heat exerted on the electrical components and that such aconfiguration makes the lamp too long.

As described above, the outer diameter of the conventionalself-ballasted fluorescent lamp has larger than the outer diameter oftypical light bulb. Therefore, this configuration presents problem inthat it is not suitable for a luminaire which uses a typical light bulbin place of a typical light bulb.

Regarding a fluorescent lamp which is used to a self-ballasedfluorescent lamp, a configuration which a bulb has a bent dischargepath, which formed by connecting a three U-shaped tubular bodies inseries and electrodes disposed at the both ends of the bulb is widelyknown. One of examples of such configuration is disclosed in JapanesePatent Laid-open No. 220360-1989. And such configuration ensures thelength of a discharge path and the reduction of the dimensions of afluorescent lamp.

In some cases, such a fluorescent lamp uses a main amalgam forcontrolling the pressure of the mercury vapor in the bulb within anappropriate range during the time that the lamp is lit under normalconditions and an auxiliary amalgam for absorbing mercury floating inthe bulb when the lamp is turned off and releasing the absorbed mercuryduring the early stage of lighting, including the moment when thelighting is initiated. In a configuration where the amalgams are used,the main amalgam is contained in a minute tube which serves to dischargethe air and projects from an end, i.e. the end at which an electrode iscontained in the bulb, of a tubular body that is located at an end ofthe bulb, while the auxiliary amalgam is disposed at an end of a tubularbody positioned at the middle portion of the bulb. However, when theexhaust minute tube that contains the main amalgam and projects from atubular body situated at an end of the bulb is located at the same endat which an electrode enclosed in the bulb is located, the temperatureof the main amalgam becomes too high due to the influence of the heatfrom the electrode. Such an increase in the temperature of the mainamalgam impairs the effective control of the pressure of the mercuryvapor and causes the pressure of the mercury vapor to increase too much,resulting in a decrease in luminous flux. This configuration presentsanother problem in that it is difficult to uniform or stabilize thepressure of the mercury vapor in the tubular body that is located at theother end of the bulb, at a long distance from the main amalgam.

Another example of fluorescent lamps characterized by inclusion of amain amalgam is disclosed in Japanese Utility Model Publication No.1992-47893, wherein a main amalgam is disposed in a minute tubeprojecting from an end of one of the three tubular bodies that form thebulb, said tubular body being the middle tubular body of the threetubular bodies. The fluorescent lamp having this configuration iscapable of reducing the influence of the heat from the electrodesexerted on the main amalgam, limiting the pressure of the mercury vaporwithin an appropriate range by preventing an excessive increase intemperature of the main amalgam, and also capable of reducing thedistances from the main amalgam to the respective ends of the bulb by anearly identical degree, thereby making the pressure of the mercuryvapor uniform and stable throughout the interior of the bulb. On theother hand, the above configuration presents a problem in that disposingthe main amalgam in the minute tube projecting from an end of the middletubular body of the three tubular bodies of the bulb positions the mainamalgam too far from the electrodes, making it difficult to warm themain amalgam. Especially at the initiation of lighting, when both theambient temperature around the fluorescent lamp and the temperature ofthe main amalgam itself are low, the main amalgam is slow to releasemercury, because it takes a long time for the temperature of the mainamalgam to reach the level where the main amalgam functions mosteffectively. As a result, the luminous flux build-up characteristicsbecome poor, and it takes an excessively long time to stabilize theluminous flux.

In response to the recent tendency toward compact fluorescent lamps, thedemands for reduction of the dimensions of bulbs are on the increase. Inthe configuration where each minute tube for discharging the air isprovided at an end of the bulb, the reduction of the diameter of thebulb makes it necessary to reduce the diameter of the minute tubes.However, a minute tube having a diameter smaller than a given dimensionhas poor exhaust conductance, resulting in decrease in the exhaustefficiency. On the other hand, if the diameter of the minute tubes arenot reduced, the distance between each minute tube and a pair of innercopper-weld wires that support an electrode is reduced, making theoperation of sealing the bulb difficult.

In order to solve the above problems, an object of the present inventionis to provide a fluorescent lamp and a self-ballasted fluorescent lampthat are characterized by the minutes tubes positioned so as to permitthe amalgams to be disposed at the optimum locations and enable thereduction of the diameter of the bulb. Another object of the presentinvention is to provide a self-ballasted fluorescent lamp and aluminaire that enable the reduction of the diameter of the portion nearthe base of the lamp as well as the reduction of the length of the lamp.Yet another object of the present invention is to provide a compactself-ballasted fluorescent lamp which is equivalent to a typical lightbulb and a luminaire including such a self-ballasted fluorescent lamp.

DISCLOSURE OF THE INVENTION

A fluorescent lamp according to the present invention includes a bulbhaving a bent discharge path, which is formed by connecting a pluralityof tubular bodies in series, and a plurality of minute tubes located atthe middle of the discharge path and communicating therewith; a phosphorapplied to the inner surface of the bulb; filler gas hermeticallycontained in the bulb; electrodes respectively disposed at the two endsof the bulb in such a manner as to be enclosed in the sealed bulb; andan amalgam enclosed in a minute tube closest to either electrode. Byenclosing the amalgam in a minute tube which is, of the plurality ofminute tubes provided at the middle portion of the bulb, located closestto either electrode, the configuration described above prevents theinfluence of the heat from the electrode from increasing the temperatureof the amalgam too much and also permits the amalgam to be warmed easilyduring the initial stage of lighting. As a result, the configuration iscapable of maintaining the pressure of the mercury vapor within anappropriate range and reducing the time taken for the luminous flux tobecome stable when lighting is initiated.

According to another feature of the invention, the fluorescent lamp hasthe same configuration as described above except that one of theelectrodes attached to the two ends of the bulb so as to be contained inthe sealed bulb is a preheating-side electrode, i.e. an electrodedisposed at the end where preheating is conducted, while the otherelectrode is a non-preheating-side electrode, i.e. an electrode disposedat the end where preheating is not conducted; and that the amalgam isenclosed in the minute tube which is closest to the preheating-sideelectrode. As a result, this configuration permits the amalgam to bewarmed easily during the initial stage of lighting and also improves thebuild-up characteristics of luminous flux.

In the configuration of a fluorescent lamp described above, by formingthe open end portion through which said minute tube communicates withthe corresponding tubular body narrower than the interior of the body ofthe minute tube, in which an amalgam will be enclosed, reliableenclosure of the amalgam is ensured.

According to yet another feature of the invention, a fluorescent lampincludes a bulb having an inner tube diameter ranging from 6 to 9 mm anda bent discharge path, which is formed by connecting a plurality oftubular bodies in series, each tubular body that is located at an end ofthe bulb being provided with a minute tube formed at the non-electrodeend of the tubular body, i.e. the end where an electrode is notdisposed; a phosphor applied to the inner surface of the bulb; fillergas hermetically contained in the bulb; and electrodes respectivelydisposed at the two ends of the bulb in such a manner as to be enclosedin the sealed bulb. By forming minute tubes for discharging the air atthe non-electrode ends of the respective tubular bodies located at thetwo ends of the bulb, the configuration described above enables aslender bulb with an inner tube, diameter ranging from 6 to 9 mm to havea minute tube having a diameter not smaller than a given dimension aswell as superior exhaust conductance and exhaust efficiency at thenon-electrode ends of the respective tubular bodies located at the twoends of the bulb. At the same time, the above configuration facilitatesan operation to dispose electrodes at the electrode-ends of the tubularbodies and seal the bulb.

In the configuration of a fluorescent lamp that has the sameconfiguration as the one described above, by enclosing an amalgam in theminute tube that is provided at the non-electrode end of a tubular bodylocated at an end of the bulb, it is possible to prevent the influenceof the heat from the electrode from increasing the temperature of theamalgam too much and also permit the amalgam to be warmed easily duringthe initial stage of lighting. As a result, it is possible to maintainthe pressure of the mercury vapor within an appropriate range and reducethe time taken for the luminous flux to become stable when lighting isinitiated.

In the configuration of a fluorescent lamp that has the sameconfiguration as the one described above, by disposing an auxiliaryamalgam in the bulb, it is possible to maintain the pressure of themercury vapor within an appropriate range and reduce the time taken forthe luminous flux to become stable when lighting is initiated.

In the configuration of a fluorescent lamp that has the sameconfiguration as the one described above, by positioning the tubularbodies of the bulb in such a manner that the tubular bodies respectivelycorrespond to the three sides of a triangle when viewed in a crosssection, the bulb can be made into such a compact shape as to be usableas a compact self-ballasted fluorescent lamp or the like.

A self-ballasted fluorescent lamp according to the present inventionincludes a fluorescent lamp and a lighting device for lighting thefluorescent lamp, said fluorescent lamp having a configurationcorresponding to any one of the configurations described above. Thisfeature of the invention is capable of providing a self-ballastedfluorescent lamp which has the same effect as one of the fluorescentlamps described above.

A self-ballasted fluorescent lamp according to the present inventionincludes an arc tube which is formed by parallely arranging a pluralityof U-shaped bent bulbs having an inner tube diameter ranging from 6 to 9mm in such a manner that the height of the bulb and the length of thedischarge path respectively range from 50 to 60 mm and from 200 to 300mm and that the lamp has a total luminous flux of not less than 700 lmand a lamp efficiency of not less than 60 lm/W when the lamp is lit atthe lamp power of 7 to 15 W; an envelope having a cover that includes abase and is adapted to permit said arc tube to be attached thereto, theheight of the envelope ranging from 110 to 125 mm including the heightof the base; and a lighting circuit contained in the cover. As thisconfiguration includes said arc tube, which is formed by parallelyarranging a plurality of U-shaped bent bulbs having an inner tubediameter ranging from 6 to 9 mm in such a manner that the height of thebulb and the length of the discharge path respectively range from 50 to60 mm and from 200 to 300 mm and that the lamp has a total luminous fluxof not less than 700 lm and a lamp efficiency of not less than 60 lm/Wwhen the lamp is lit at the lamp power of 7 to 15 W, and limits theheight the envelope, which is provided with a cover including a base towhich the arc tube is attached, in the range from 110 to 125 mm, it ispossible to determine the optimum criteria for the components to makethe dimensions and the total luminous flux of the lamp correspond tothose of a typical light bulb for general illumination, such as anincandescent lamp having a rated power of 60 W type. The lower limit ofthe inner tube diameter of the tube is set at 6 mm as mentioned above,because the tube having an inner tube diameter of less than 6 mmrequires a considerably high starting voltage and is thereforeimpractical. The term ‘a total luminous flux’ mentioned above refers toa value representing radiation from an entire self-ballasted fluorescentlamp. Therefore, if the self-ballasted fluorescent lamp includes aglobe, it represents the result of a measurement conducted in the statewhere the globe is attached. Furthermore, ‘a lamp efficiency’ is definedas a value based on the lamp power minus the power consumption of thelighting circuit.

According to yet another feature of the invention, a self-ballastedfluorescent lamp includes an arc tube formed by parallely arranging aplurality of U-shaped bent bulbs, each of which has an outer tubediameter ranging from 8 to 11 mm, a tube wall thickness ranging from 0.7to 1.0 mm and a smoothly curved crown; a cover including a base that isadapted to permit said arc tube to be attached thereto; and a lightingcircuit contained in the cover. As this configuration includes said arctube formed by parallely arranging a plurality of U-shaped bent bulbs,each of which has an outer tube diameter ranging from 8 to 11 mm, a tubewall thickness ranging from 0.7 to 1.0 mm and a smoothly curved crown,it is possible to determine such a tube diameter as to make thedimensions and the total luminous flux of the lamp correspond to thoseof a typical light bulb for general illumination, such as anincandescent lamp having a rated power of 60 W type and also determinesuch a range of the thickness of the bulb wall as to enable the increaseof the inner surface area of the bulb while ensuring sufficient strengthwithin the limit of the outer diameter of the bulb determined as above.Further, in order to form each U-shaped bent bulb within the limit ofthe tube wall thickness determined as above, the crown of the U has tobe smoothly curved. Should the crown have a sharp corner or corners, thetube wall at the corner(s) would be too thin to maintain sufficientstrength.

According to yet another feature of the invention, a self-ballastedfluorescent lamp includes an arc tube formed by parallely arranging aplurality of U-shaped bent bulbs, each of which has a bent portion andstraight portions; a cover including a base that is adapted to permitsaid arc tube to be attached thereto; and a lighting circuit whichincludes a circuit board having the maximum width ranging up to 1.2times the maximum width of the arc tube, the maximum width of the arctube being the dimension along which the U-shaped bent bulbs arearranged, said lighting circuit contained in the cover in such a mannerthat the circuit board is positioned with one of its sides facing allthe ends of the straight portions of the arc tube and provided withcomponents having relatively high heat resistance mounted on the side ofthe circuit board facing the arc tube and components having relativelylow heat resistance mounted on the opposite side of the circuit board.According to the configuration as above, the maximum width of thecircuit board is so set as to range up to 1.2 times the maximumdimension along which the U-shaped bent bulbs of the arc tube arearranged, and the components that have relatively high heat resistanceare mounted on the arc tube facing side of the circuit board, while thecomponents having relatively low heat resistance are mounted on theother side of the circuit board. Thus, the above configuration iscapable of reducing the size of the circuit board while limiting theinfluence that heat exerts on the components mounted on the circuitboard. Consequently, the configuration is capable of reducing thedimensions of the cover, which contains the circuit board, so that theyare equivalent to the dimensions of a typical light bulb. Although it isrecommended that the circuit board have a shape of a circular disk,which is the most effective shape to ensure the space for mounting, thecircuit board may have a polygonal shape, such as a square, or an ovalshape.

According to yet another feature of the invention, the components havingrelatively high heat resistance of the fluorescent lamp described aboveare chip-shaped rectifying devices. Therefore, the thermal influencefrom the arc tube can be limited.

According to yet another feature of the invention, a self-ballastedfluorescent lamp includes a cover having a base; a lighting circuitcontained in the cover; a globe having a nearly identical shape as atypical light bulb and attached to the cover, and an arc tube which iscontained in the globe and has three or more U-shaped bent bulbs, eachof which has a smoothly curbed crown, the U-shaped bent bulbs connectedto one another in series and arranged so that their crowns are alignedin a circle and face the inner surface of the globe and that theU-shaped bent bulbs are spaced apart at a distance not exceeding theouter diameter of each bulb. As the arc tube has three or more U-shapedbent bulbs which have smoothly curbed crowns, are connected to oneanother in series, and positioned apart from one another in such amanner that the distance between the bulbs does not exceed the outerdiameter of each bulb and that their crowns are aligned in a circle andface the inner surface of the globe, this configuration makes itpossible to dispose the arc tube in the globe that is formed in acompact shape resembling a typical light bulb. This configuration isalso capable of providing more uniform luminosity and more effectiveillumination even if the arc tube is contained in such a compact globe.

According to yet another feature of the invention, a self-ballastedfluorescent lamp includes an arc tube formed by parallely arranging aplurality of U-shaped bent bulbs having an outer tube diameter rangingfrom 8 to 11 mm, the maximum width of the arc tube along which theU-shaped bent bulbs are arranged ranging from 32 to 43 mm; a coverincluding a base that is adapted to permit said arc tube to be attachedthereto; a lighting circuit contained in the cover; and a globe having amaximum outer diameter limited in the range from 55 to 60 mm andattached to the cover with said arc tube enclosed in the globe in such amanner that A2>A1≧A3, wherein A1 represents the minimum distance betweenthe globe and each crown of the arc tube, A2 the minimum distancebetween the maximum diameter portion of the globe and the arc tube, andA3 the minimum distance between the base end of the globe and the arctube. As a self-ballasted fluorescent lamp includes an arc tube formedby parallely arranging a plurality of U-shaped bent bulbs having anouter tube diameter ranging from 8 to 11 mm, the maximum width of thearc tube along which the U-shaped bent bulbs are arranged ranging from32 to 43 mm, and a globe having a maximum outer diameter limited in therange from 55 to 60 mm and attached to the cover with the arc tubeenclosed in the globe in such a manner that A2>A1≧A3, wherein A1represents the minimum distance between the globe and each crown of thearc tube, A2 the minimum distance between the maximum diameter portionof the globe and the arc tube, and A3 the minimum distance between thebase end of the globe and the arc tube, the feature of the inventiondescribed above enables the determination of the optimum criteria forluminous intensity distribution in the direction of the sides and thecrown of the arc tube.

The above configuration increases the luminous intensity distributed inthe direction of the base and is therefore particularly effective inbringing the characteristics of luminous intensity distribution of thelamp into close proximity to those of an incandescent lamp. As a result,the lamp can be illuminated as if it were an incandescent lamp and usedfor a luminaire that is designed for an incandescent lamp without givingany disagreeability.

As the outer diameter of the globe or the diameter of the portion of thecover where the base is located has to be limited to no larger than 45mm in order to make the lamp resemble a typical light bulb and moresuitable to be fitted in a luminaire that uses a typical light bulb, theupper limit of the maximum width of the arc tube along which theU-shaped bent bulbs are arranged is set at 43 mm, taking the clearancebetween the inner surface of the globe or the cover and the outercircumferential surface of the arc tube into consideration. In caseswhere a self-ballasted fluorescent lamp is installed in a luminairedesigned for a typical light bulb, limiting the outer diameter of theglobe or the diameter of the portion of the cover where the base islocated to no larger than 45 mm presents such other benefits as ensuringa wide clearance between the lamp and the other components of theluminaire, thereby enabling the radiation under good conditions.

By setting A1 in the range from 2 to 8 mm, A2 in the range from 3 to 13mm and A3 in the range from 2 to 8 mm in the configuration of theself-ballasted fluorescent lamp described above, the optimum criteriafor distributing light toward the sides and the crown of the arc tubecan be determined.

By forming the self-ballasted fluorescent lamp described above so as tohave an outer shape resembling a typical light bulb for generalillumination, the invention permits the lamp to be mounted in aluminaire designed for a typical light bulb, thereby expanding the rangeof usage. As the self-ballasted fluorescent lamp having an outer shaperesembling a typical light bulb can be mounted in such a luminairewithout giving any disagreeability, the invention is also capable ofimproving the appearance of the self-ballasted fluorescent lamp. Theterm ‘light bulb for general illumination’ mentioned above means a lightbulb defined as JIS Standard C 7501. In cases where a self-ballastedfluorescent lamp is provided with a globe, it is desirable that theshape of the outline of the globe be similar to the glass light bulb ofa typical light bulb.

As yet another feature of the invention, bonding the arc tube, the globeand the supporting member supporting the arc tube of a self-ballastedfluorescent lamp having the configuration as above to one another bymeans of a bonding agent permits the heat to be efficiently radiatedfrom the arc tube through the globe and also simplifies the structure,thereby enabling the reduction of the production costs.

Furthermore, by arranging the U-shaped bent bulbs of the arc tube of aself-ballasted fluorescent lamp having the configuration as above insuch a manner that their cross sections give the appearance of atriangle, the arc tube can be arranged in a compact shape.

By setting the distance w1 between the two straight portions of eachU-shaped bent bulb of a self-ballasted fluorescent lamp having theconfiguration as above to be nearly identical to the distance w2 betweeneach straight portion of a U-shaped bent bulb and the U-shaped bent bulbthat is adjacent to said straight portion, and respectively limiting thedistances w1, w2 in the range from 1 to 5 mm, the arc tube can bearranged in a compact shape. Although the distances w1, w2 may be set atany desired dimensions on condition of being in the range from 1 to 5mm, it is desirable for production reasons that they be in the rangefrom 2 to 3 mm. Further, a distance that exceeds 5 mm may make itimpossible to produce a compact lamp.

According to yet another feature of the invention, the lighting circuitof a self-ballasted fluorescent lamp having the configuration as aboveincludes a half-bridge type inverter main circuit having at least a pairof transistors consisting of an N-channel transistor and a P-channeltransistor, which are connected in series with each other to an inputpower supply and serve as the main switching element for generating ahigh frequency voltage; a ballast choke connected to the inverter maincircuit so as to light the arc tube in stable conditions; and a controlmeans which has a secondary winding magnetically connected to theballast choke and shared by the N-channel transistor and the P-channeltransistor so that the control means serves to control the transistorsby means of the secondary winding. With the configuration as above,wherein the control means operates the N-channel transistor and theP-channel transistor, the invention enables the control of a pluralityof transistors under different conditions based on output from a singlecontrol means, thereby simplifying the configuration of the circuit. Byusing a lighting circuit which requires only a minimal number of partsas described above, the dimensions of the self-ballasted fluorescentlamp can be further reduced.

According to yet another feature of the invention, a self-ballastedfluorescent lamp includes an arc tube; a cover having a base; and alighting circuit that has a circuit board and electrical componentsmounted on both sides of the circuit board in such a manner that thecircuit board is contained in the cover and faces the ends of the arctube and that the electrical components mounted on the side facing thearc tube are so positioned as to not be aligned with the ends of the arctube. By so positioning the circuit board as to face the ends of the arctube and mounting electrical components on both sides of the circuitboard, the configuration described above is capable of reducing thedimensions of the circuit board and, consequently, reducing the diameterof the portion of the lamp near the base. Furthermore, by so arrangingelectrical components mounted on the side facing the arc tube as to notbe aligned with the ends of the arc tube, the configuration is capableof preventing interference of the arc tube with the electricalcomponents, limiting the influence of the heat from the arc tube, andreducing the length of the lamp.

According to yet another feature of the invention, a self-ballastedfluorescent lamp includes an arc tube; a cover having a base; and alighting circuit and a lighting circuit that has a circuit board andelectrical components mounted on both sides of the circuit board in sucha manner that the circuit board is contained in the cover and faces theends of the arc tube and that the electrical components mounted on theside facing the arc tube are so positioned as to not be aligned with theminute tubes of the arc tube. By so positioning the circuit board as toface the ends of the arc tube and mounting electrical components on bothsides of the circuit board the configuration described above is capableof reducing the dimensions of the circuit board and, consequently,reducing the diameter of the portion near the base. Furthermore, by soarranging electrical components mounted on the side facing the arc tubeas to not be aligned with the minute tubes of the arc tube, theconfiguration is capable of preventing interference of the minute tubesthat project further from the arc tube with the electrical components,limiting the influence of the heat from the arc tube, and reducing thelength of the lamp.

By forming a self-ballasted fluorescent lamp having the configurationdescribed above in such a manner that the outer diameter of the circuitboard is nearly identical to the inner diameter of the cover, theinvention makes it possible to arrange components with the space insidethe cover used to the full extent and, consequently, reduce the diameterof the portion near the base.

In the configuration of a self-ballasted fluorescent lamp describedabove, by positioning the electrical components mounted on the sidefacing the arc tube apart from the electrodes of the arc tube, theinfluence that the heat generated by the electrodes exerts on theelectrical components can be limited.

A luminaire according to the invention is provided with a self-ballastedfluorescent lamp which has any one of the configurations describedabove. Using a compact self-ballasted fluorescent lamp according to theinvention enables the use of a luminaire designed for a typical lightbulb. The invention also enables the reduction of the diameter of theportion of the self-ballasted fluorescent lamp near the base and thelength of the lamp, the use of a socket designed for an incandescentlamp without any disagreeability, the reduction of production costs andthe improvement of the appearance.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a side view of a self-ballasted fluorescent lamp according toa first embodiment of the present invention, wherein the globe of thelamp is illustrated as if the inside contents were visible;

FIG. 2 is a bottom view of same, wherein the globe of the lamp isillustrated as if the inside contents were visible;

FIG. 3 is a sectional view of a part of said self-ballasted fluorescentlamp;

FIG. 4 is a side view of a U-shaped bent bulb of said self-ballastedfluorescent lamp;

FIG. 5 is a sectional view of a part of said U-shaped bent bulb;

FIG. 6 is a graph showing the relationship among outer tube diameters ofsaid U-shaped bent bulb, lamp efficiencies and maximum widths of the arctube;

FIG. 7 is a schematic illustration to explain the arrangement of saidU-shaped bent bulb;

FIG. 8 is a circuit diagram of a lighting circuit of said lamp;

FIG. 9 is a side view of a partially-cutaway self-ballasted fluorescentlamp according to a seventh embodiment of the present invention;

FIG. 10 is a side view of a partially-cutaway self-ballasted fluorescentlamp according to an eighth embodiment of the present invention;

FIG. 11 is a sectional view of a part of a partially-cutawayself-ballasted fluorescent lamp according to a ninth embodiment of thepresent invention;

FIG. 12 is a perspective of a part of said self-ballasted fluorescentlamp; and

FIG. 13 is a schematic illustration of said self-ballasted fluorescentlamp as viewed from the bottom. Furthermore,

FIG. 14 illustrates a fluorescent lamp according to a tenth embodimentof the present invention, wherein (a) is an exploded view of a bulb ofthe fluorescent lamp, and (b) is an enlarged sectional view of the partA in FIG. 14 (a).

FIG. 15 is a side view of said fluorescent lamp;

FIG. 16 is a top view of same, wherein the globe of said fluorescentlamp is illustrated as if the inside contents were visible;

FIG. 17 is a sectional view of a part of said fluorescent lamp;

FIG. 18 is an exploded view of a bulb of a fluorescent lamp according toan 11th embodiment of the present invention;

FIG. 19 is a circuit diagram of a lighting circuit of said fluorescentlamp; and

FIG. 20 is a top view of a fluorescent lamp according to a 12thembodiment of the present invention, wherein the globe of saidfluorescent lamp is illustrated as if the inside contents were visible.

BEST MODE FOR CARRYING OUT THE INVENTION

Next, a fluorescent lamp, a self-ballasted fluorescent lamp and aluminaire according to an embodiment of the present invention areexplained hereunder, referring to the drawings.

A first embodiment of the present invention is shown in FIGS. 1 through5, wherein FIG. 1 is a side view of the self-ballasted fluorescent lampwith the globe of the lamp illustrated as if the inside contents werevisible; FIG. 2 is a bottom view of same with the globe of the lampillustrated as if the inside contents were visible; FIG. 3 is asectional view of a part of the self-ballasted fluorescent lamp; FIG. 4is a side view of a U-shaped bent bulb; and FIG. 5 is a sectional viewof a part of said U-shaped bent bulb.

Referring to FIGS. 1 through 3, numeral 10 denotes a self-ballastedfluorescent lamp, comprising a cover 14 having a base 12, a lightingcircuit 16 contained in the cover 14, a translucent globe 17, and an arctube 18 contained in the globe 17. The globe 17 and the cover 14 form anenvelope 19 that has such an outer shape as to have nearly the samedimensions as standard dimensions of an electric light bulb for generalillumination, e.g. a 60 W-type incandescent lamp. In other words, theheight H1 of the envelope 19 ranges from approximately 110 to 125 mmincluding the base 12; the diameter D1, i.e. the outer diameter; and theouter diameter D2 of the cover 14 is approximately 40 mm. The term‘electric light bulb for general illumination’ mentioned above means alight bulb defined as JIS Standard C 7501. Further, in the explanationhereunder, the side where the base 12 is located is referred to as theupper side, while the side where the globe 17 is located is referred toas the lower side.

The cover 14 is provided with a cover body 21 that may be formed of aheat resistant synthetic resin such as polybutylene terephthalate (PBT).The cover body 21 has an approximately cylindrical shape that flaresdownward. The base 12, which may be of the E26 type, is disposed overthe top of the cover body 21 and fastened thereto with a bonding agent,or by such other means as crimping.

The globe 17 may be transparent or photo-diffusing milky white. Theglobe 17 is formed of glass, synthetic resin or the like into a smoothlycurved shape nearly identical to the glass bulb of a typical light bulbhaving a rated power consumption of approximately 60 W . The edge of theopening of the globe 17 is formed into a fitting edge 17 a to be fittedin an opening at the bottom of the cover 14. The luminance of the lampmay be made more uniform by forming the globe 17 in combination withanother member, such as a diffusion film.

As shown in FIGS. 1 and 3, the lighting circuit 16 contained in thecover 14 has a disk-shaped circuit board 24 disposed horizontally, inother words perpendicularly to the lengthwise direction of the arc tube18. A plurality of electrical components 25, 26 are respectively mountedon both sides of the circuit board 24, i.e. the upside facing the base12 and the underside facing the arc tube 18, thereby forming an invertercircuit (a high-frequency lighting circuit) for conducting highfrequency lighting.

Of the of electrical components 25, 26 mentioned above, the electricalcomponents 25 mainly consisting of components having relatively low heatresistance, such as electrolytic condensers and film condensers, aremounted on the upper face of the circuit board 24, while electricalcomponents 26 consisting of thin, small chip-shaped rectifiers,rectifying devices or diode bridges having relatively high heatresistance, transistors, resistors, etc. that are arranged in a packageapproximately 2 to 3 mm in thick are mounted on the underside of thecircuit board 24.

The circuit board 24 has a shape resembling a disk whose diameter, i.e.the maximum width, ranges up to 1.2 times the maximum dimension alongwhich the U-shaped bent bulbs are arranged. A total of four circuit-sidewires 28 adapted to serve as the output unit are arranged in two pairsand drawn out of the circuit board 24. Instead of providing thecircuit-side wires 28, wrapping pins may be set in the circuit board 24.

As shown in FIGS. 1 through 5, the arc tube 18 contained in the globe 17consists of three U-shaped bent bulbs 31 that have nearly identicalshapes and arranged at given locations. The three U-shaped bent bulbs 31are connected to one another via communicating tubes 32 so as to form asingle discharge path. Each U-shaped bent bulb 31 is provided with aphosphor film, which is formed on the inner surface of the U-shaped bentbulb 31, and hermetically contained a rare gas, such as argon, andmercury. Each U-shaped bent bulb 31 is a cylindrical bulb made of glasshaving an outer tube diameter d1 ranging from 8 to 11 mm, an inner tubediameter d2 ranging from 6 to 9 mm, a thickness of the tube wall rangingfrom 0.7 to 1.0 mm and a length ranging from approximately 110 to 130mm. Each U-shaped bent bulb 31 is formed into a smoothly curved U-likeshape having a crown P by bending said glass bulb at the middle portionso that the bulb 31 has a bent portion 31 a that is smoothly turned backon itself and a pair of straight portions 31 b extending parallel toeach other and integrally connected to the bent portion 31 a. The heightH2 of the bulbs of the arc tube 18 formed as above ranges from 50 to 60mm; the length of the discharge path ranges from 200 to 300 mm; and themaximum width along which the bulbs are arranged, i.e. the dimensionrepresented by D3 in FIG. 1, ranges from 32 to 43 mm.

The arc tube 18 is fastened to a partition plate 33, which may bereferred to as a supporting member in the claims or other parts of thespecification and serves as a fluorescent lamp fastening member as wellas a lighting circuit fastening member. The partition plate 33 isfastened to the cover 14. To be more specific, the partition plate 33has a disk-shaped base portion 34 which is provided with mounting holes34 a. The arc tube 18 is fastened to the partition plate 33 with theends of the U-shaped bent bulbs 31 respectively inserted into themounting holes 34 a and secured therein by means of, for example,bonding the regions of the bulbs to the base portion with an adhesiveagent. A fitting step portion 35 that extends upward and then outward isformed around the outer edge of the base portion 34. These members arefastened to one another by fitting the fitting step portion 35 in thecover 14 and filing the gap between the fitting step portion 35 and thecover 14 with a bonding agent 37 in such a state that the fitting edge17 a of the globe 17 is fitted between the fitting step portion 35 andthe cover 14. A mounting edge 38 that may have a cylindrical shape risesfrom the top of the fitting step portion 35, and the circuit board 24 ofthe lighting circuit 16 is fitted, bonded or otherwise attached to themounting edge 38.

When the self-ballasted fluorescent lamp 10 is assembled in the mannerdescribed above, the arc tube 18 is housed in the globe 17 at a givenposition. To be more specific, in the state where the self-ballastedfluorescent lamp 10 is assembled, the crowns P of the U-shaped bentbulbs 31 are aligned at regular intervals in a circle whose center is onthe central axis of the self-ballasted fluorescent lamp 10 extending inthe vertical direction, and the straight portions 31 b of the U-shapedbent bulbs 31, too, are aligned at regular intervals in a circle whosecenter corresponds to the central axis of the lamp. In other words, asshown in FIG. 7, the tube axes of the straight portions 31 b of thethree U-shaped bent bulbs 31 are respectively located at the approximatevertexes of a regular hexagon. The distance w1 between the two straightportions 31 b of each U-shaped bent bulb 31 is nearly identical to thedistance w2 between each straight portion 31 b and the U-shaped bentbulb 31 adjacent to said straight portion 31 b, and the distances w1, w2are in the range between 1 mm and 5 mm. Although the distances w1, w2may be set at any desired values on condition of being in the range from1 to 5 mm, it is desirable for production reasons that they are in therange between 2 mm and 3 mm. Further, a distance that exceeds 5 mm maymake it impossible to produce a compact lamp.

Referring to FIGS. 6 and 7, the reason for setting the maximum width aof the aforementioned arc tube 18 in the range from the 32 to 43 mm andthe outer tube diameter d1 of each U-shaped bent bulb 31 in the rangefrom 8 to 11 mm is explained hereunder.

FIG. 6 shows the lamp efficiency in the case where the thickness of thetube wall of the arc tube 18, the gas pressure, the length of thedischarge path and the lamp current are respectively set at 0.8 mm, 400Pa, 250 mm and 0.2 A, and also shows the relationship between themaximum width a and the outer tube diameter d1 of each U-shaped bentbulb 31 regarding the exemplary configurations where the distances w arerespectively 5 mm and 2 mm.

In order to make the lamp resemble a typical light bulb and moresuitable to be fitted in a luminaire that uses a typical light bulb, theouter diameter of the glove 17 has to be 45 mm or less (around 40 mmbeing most desirable). In case of the present embodiment, the upperlimit of the maximum width a df the arc tube 18 is set at 43 mm, takingthe clearance between the inner surface of the globe 17 or the cover 14and the outer circumferential surface of the arc tube 18 intoconsideration.

The lower limit of the outer tube diameter d1 is set at 8 mm, where therelative lamp efficiency becomes 97% or more.

The upper limit of the outer tube diameter d1 is determined based on theequation a=3d1+2w, wherein the upper limit of the maximum width a of thearc tube 18 is 43 mm. It has to be noted that the tube axes of thestraight portions 31 b of the three U-shaped bent bulbs 31 of the arctube 18 are respectively located at the approximate vertexes of aregular hexagon. In other words, w1 and w2 are nearly equal. Therefore,the upper limit of the outer tube diameter d1 is set at 11 mm byreplacing the variables in the equation a=3d1+2w with the maximumdimensions, in other words by replacing ‘a’ and ‘w’ with 43 and 5respectively, and finding the value of d1 from the equation 43=3d1+2×5.

The lower limit of the maximum width a of the arc tube 18 is set at 28mm by replacing the variables in the equation a=3d1+2w with the minimumdimensions, in other words by replacing “d1” and “w” with 8 and 2respectively, and finding the value of a from the equation a

The lower limit of the inner tube diameter is set at 6 mm, because theinner tube diameter of less than 6 mm would result in an excessivelyhigh starting voltage and therefore be not practical.=3×8+2×2.

Should the thickness of the tube wall be 1.1 mm or more, the glassmaterial tends to accumulate at the inside of the U-shaped curvedportions 31 a, making such portions prone to cracks. Such anaccumulation of glass can be limited by setting the thickness of thetube wall to be in the range between 0.7 mm and 1.0 mm. Given that theminimum clearance between the globe 17 and each crown P of the arc tube18 is A1; the minimum clearance between the portion where the outerdiameter of the globe 17 is the greatest and the arc tube 18 is A2; andthat the minimum clearance between the base end of the globe 17 and thearc tube 18 is A3, the relationship among them has to be as shown in therepresentation: A2>A1≧A3, wherein A1, A2 and A3 are respectively in theranges from approximately 2 to 8 mm, from approximately 3 to 13 mm andfrom approximately 2 to 8 mm. By setting the relative dimensions such asA2>A1≧A3, the distribution of luminous intensity can be made such thatthe light distributed to the crowns is more intense. Furthermore, bysetting A1 such as A2>A1≧A3, i.e. 2 mm>A1≧8 mm, the light distributed tothe crowns can be further intensified, in other words the optimumcriteria for luminous intensity distribution to the side wall and thecrown of the arc tube 18 can be obtained. Using a luminance meter (BM-8manufactured by TOPCON CORP.), the surface luminance of the globe 17 wasmeasured to be 380 cd/m². Results of the experiment also indicated thatthe total light flux amounted to be 810 lm.

One of the two ends of each U-shaped bent bulb 31 is sealed by means ofa line seal with a mount, a pinch seal without a mount, or the like. Aminute tube 41 that may otherwise be called an exhaust tube is welded tothe other end of each U-shaped bent bulb 31 to discharge the air. Theminute tube 41 is designed such that it may be provided with an amalgam42 if it is necessary. A filament coil 44 is disposed at the end of eachU-shaped bent bulb 31 that is located at an end of the arc tube 18 insuch a state that each filament coil 44 is supported between a pair ofcopper-weld wires (lead-in wires) 45 by use of a line seal with a mountor the like. Via each respective dumet wire 46 attached to the glass atthe end of the U-shaped bent bulb 31 and thus sealed in the bulb, eachcopper-weld wire 45 is connected to a lamp wire 48 that is drawn out ofthe U-shaped bent bulb 31. If it is necessary, one of the copper-weldwires 45 may be provided with an auxiliary amalgam 49.

As shown in FIG. 3, the four lamp wires 48 that are arranged in twopairs and drawn out of the arc tube 18 are electrically and mechanicallyconnected to the lighting circuit 16 as they are twisted with circuitwires 28 that are drawn from the lighting circuit 16. Each set of wires28, 48 are inserted into a groove formed in the rib-like mounting edge38 of the partition plate 33, and thus guided by the groove. Comparedwith a structure that calls for providing the lighting circuit 16 with aconnector and inserting the lamp wires 48 into the connector toelectrically connect the wires to the lighting circuit 16, or anotherstructure that calls for electrically connecting the lamp wires 48 bywrapping the wires around column-shaped pins that are projected from thelighting circuit 16, the configuration according to the embodimentdescribed above requires only a limited space and therefore is capableof reducing the dimensions of the lamp. Furthermore, as there is no needof parts dedicated for the connection, the embodiment also ensures easy,reliable connection of wires at a low cost. Should there be a greatdifference between the diameters of each circuit wire 28 and lamp wire48, such a difference makes a twisting operation difficult. Therefore,it is desirable to set the relative dimensions of the wires, i.e. thediameter D28 of each circuit wire 28 and the diameter D48 of each lampwire 48, to be (0.9×D28)<D48<(1.1×D28) to ensure easy and reliableconnection. The electrical and mechanical connection of the wires can bemade even more reliable by twisting the wires no fewer than three turns.In an alternative configuration wherein members in the shape of acylindrical pin are projected upward from the partition plate 33, eachpair of wires 28, 48 may be connected by twisting around one of thesecylindrical members.

In cases where the inner tube diameter d3 of the minute tube 41 of eachU-shaped bent bulb for discharging gas from the U-shaped bent bulb istoo small with respect to the inner tube diameter d2 of the U-shapedbent bulb 31, it is necessary to increase the duration of gas dischargedue to the poor exhaust efficiency. In cases where the minute tube 41has an excessively large diameter, it is impossible to provide asufficient clearance between the outer surface of the minute tube 41 orthe inner surface of the U-shaped bent bulb 31 and each copper-weld wire45, which is attached to and sealed in the bulb at the same time whenthe minute tube 41 is attached. Such a lack of a sufficient clearancetends to cause an improper attachment or other problems, often degradingthe quality of the arc tube 18. A U-shaped bent bulb of a conventionallamp, in particular, has an inner tube diameter more than three times aslarge as the inner tube diameter of its minute tube 41, making itdifficult to improve the air discharge efficiency, because the minutetube 41 for discharging the air is disposed at one of the lengthwiseends of the arc tube in many cases. In order to solve this problem, thepresent embodiment calls for setting the inner tube diameter d3 of eachminute tube 41, with respect to the inner tube diameter d2 of theU-shaped bent bulb 31, to be within the range 2.0<(d2/d3)<2.8. Thusincreasing the inner tube diameter d3 of the minute tubes 41 improvesthe quality of the arc tube 18 by increasing the air dischargeefficiency as well as ensuring the reliable sealing and attachment ofthe minute tubes 41. Furthermore, the minute tubes 41 serving as exhaustpipes may be disposed about the middle of the length of the arc tube 18to increase the air discharge efficiency.

The self-ballasted fluorescent lamp 10 structured as above has suchcharacteristics that, when a rated input power is 14 W, a high frequencypower of 12.5 W is applied to the arc tube 18, producing a lamp currentof 280 mA, a lamp voltage of 65 V and a total luminous flux of 810 lm,which results from the use of the three band phosphor.

FIG. 8 is a circuit diagram illustrating the configuration of thelighting circuit 16. The lighting circuit 16 has an input power unit E.The input power unit E includes a condenser C1 which constitutes afilter and is connected to a commercial AC power supply e via a fuse F1,and a full-wave rectifying circuit 51 whose input terminal is connectedto the condenser C1 via an inductor L1 that constitutes a filter. Asmoothing condenser C2 is connected to the output terminal of thefull-wave rectifying circuit 51 via a resistor R1, and an inverter maincircuit 52 of a half-bridge type is connected to the condenser C2.

The inverter main circuit 52 comprises a series circuit of field effecttransistors Q1, Q2 serving as a switching element is connected inparallel with the condenser C2. The field effect transistor Q1 is anN-channel transistor of the MOS type, while the field effect transistorQ2 is a P-channel transistor of the MOS type. The source of theN-channel field effect transistor Q1 and the source of the P-channelfield effect transistor Q2 are connected to each other.

An end of each one of the filament coils 44, 44, which are respectivelydisposed at the two ends of the arc tube 18, is connected to a pointbetween the drain and the source of the field effect transistor Q2 via aballast choke L2 and a condenser C3 for interrupting direct current. Incase of the present embodiment, the ballast choke U also serves togenerate resonance. A start-up condenser C4 is disposed between andconnected to the aforementioned one end of the one of the filament coils44, 44 and the other end of the other filament coil 44. An activatingresistor R2 which forms a part of an activating circuit 53 is connectedto the gate of the field effect transistor Q1, the gate of the fieldeffect transistor Q2, and the junction point where the resistor R1 andthe condenser C2 are connected. A series circuit of a condenser C5 and acondenser C6 is disposed between and connected to the gates of the fieldeffect transistors Q1, Q2 and the sources of the field effecttransistors Q1, Q2. A series circuit which consists of a Zener diode ZD1and a Zener diode ZD2 and serves to protect the gates of the fieldeffect transistors Q1, Q2 is connected in parallel with a series circuitconsisting of the condenser C5 and the condenser C6. The condenser C6forms a part of a control circuit 54 that serves as a control means. Theballast choke L2 is provided with a secondary winding L3, which ismagnetically joined to the ballast choke L2 and connected to a resonancecircuit 56 that consists of an inductor L4 and the condenser C6.Furthermore, a resistor R3 of the activating circuit 53 is connected inparallel to a series circuit consisting of the condenser C5 and theinductor L4.

A parallel circuit consisting of a resistor R4 of the activating circuit53 and a condenser C7 is disposed between and connected to the drain andthe source of the field effect transistor Q2. Said condenser C7 servesto improve the switching function.

The field effect transistors Q1, Q2 may be of a bipolar type. Theinverter main circuit 52 may have two or more pairs of seriallyconnected switching elements. One of the examples of such aconfiguration is a full-bridge type. Furthermore, it does not matterwhether the arc tube 18 is of a type which calls for preheating bothfilament coils 44 or a type wherein neither filament coil 44 ispreheated.

With the configuration as above, when the power is fed into the lightingcircuit 16, the voltage on the commercial AC power supply e is rectifiedover the full wave by the full-wave rectifying circuit 51 and smoothedby the condenser C2.

The voltage is applied through the resistor R2 to the gate of theN-channel field effect transistor Q1, thereby turning on the fieldeffect transistor Q1. As a result, a voltage is applied to the circuitconsisting of the ballast choke L2, the condenser C3 and the condenserC4 so that the bast choke L12 and the condenser C4 generate resonance.As a voltage is induced on the secondary winding L3 of the ballast chokeL2, intrinsic resonance between the inductor LA and the condenser C6 ofthe control circuit 54 is generated, thereby generating such a voltageas to turn on the field effect transistor Q1 and turn off the fieldeffect transistor Q2. When the resonance voltage between the ballastchoke L2 and the condenser C4 is inverted thereafter, a voltage which isthe reverse of the aforementioned voltage is generated on the secondarywinding L3 so that the control circuit 54 generates such a voltage as toturn off the field effect transistor Q1 and turn on the field effecttransistor Q2. Then, when the resonance voltage between the ballastchoke L2 and the condenser C4 is inverted, the field effect transistorQ1 is turned on, while the field effect transistor Q2 is turned off.Thereafter, the field effect transistor Q1 and the field effecttransistor Q2 are alternately turned on and off in the same manner asabove to generate resonance voltage so that a starting voltage isapplied to the arc tube 18 that is connected in parallel with thecondenser C4, while one of the filament coils 44 is preheated. Thus, thearc tube 18 is started and becomes illuminated.

The Zener diode ZD1 and the Zener diode ZD2 unify the voltages on thegates of the field effect transistor Q1 and the field effect transistorQ2 and also protect the gates from an excessively high voltage.

Therefore, by using the N-channel field effect transistor Q1 and theP-channel field effect transistor Q2 and connecting the N-channel fieldeffect transistor Q1 to the side where the electric potential is higher,both the N-channel field effect transistor Q1 and P-channel field effecttransistor Q2 can be controlled by a single control circuit, i.e. thecontrol circuit 54. As the control circuit 54 is provided with aresonance circuit consisting of the inductor LA and the condenser C6,the size of the control circuit 54 can be reduced by reducing the numberof the turns of the secondary winding L3, and it is also possible toreduce the difference between the voltage output from the controlcircuit 54 when no load is applied and the voltage output from thecontrol circuit 54 under a load. If the resonance circuit consisting ofthe inductor LA and the condenser C6 is omitted so that the outputvoltage from the secondary winding L3 is directly output, there may be amore than 10-fold difference in voltage output from the secondarywinding 13 during no-load period and voltage output during on-loadperiod. Although the magnitude of the difference depends on therelationship between the start-up voltage and the lamp voltage on thearc tube 18, such a large difference may either make it difficult forZener diodes to perform unification of the gate voltages and protectionof the gates or require expensive kinds of Zener diodes.

The present embodiment includes an arc tube 18 comprised of a pluralityof U-shaped bent bulbs 31 having an inner tube diameter of 6 to 9 mm andarranged in parallel to one another in such a way that the height H2 ofthe bulb ranges from 50 to 60 mm; the length of the discharge pathranges from 200 to 300 mm; and that the total luminous flux is 700 lmwhen the lamp is lit at the lamp power of 7 to 15 W. By limiting theheight H1 of the envelope 19 that is provided with the cover 14 withinthe range from 110 to 125 mm including the height of the base 12, towhich said arc tube 18 is attached, the optimum criteria for thecomponents can be determined in order to make the dimensions and thetotal luminous flux of the lamp correspond to those of a typical, 60 W-type light bulb for general illumination. The lower limit of the innertube diameter of the tube is set at 6 mm as mentioned above, because thetube having an inner tube diameter of less than 6 mm requires aconsiderably high starting voltage and is therefore impractical.

As the embodiment includes an arc tube 18 comprised of a parallelyarranged plurality of U-shaped bent bulbs 31, each of which has an outertube diameter of 8 to 11 mm, a bulb wall from 0.7 to 1.0 mm thick and acurved crown P, it is possible to determine the tube diameter so thatthe dimensions and the total luminous flux of the lamp correspond tothose of a typical, 60 W -type light bulb for general illumination andalso determine the range of the thickness of the bulb wall which enablesthe increase of the inner surface area of the bulb while ensuringsufficient strength within the limit of the outer diameter of the bulbdetermined as above. Should the bulb wall have a thickness of 1.1 mm ormore, the inner diameter of the bulb becomes too small with respect tothe outer diameter of the bulb. Not only does this make it impossible toincrease the inner surface area but also causes glass to accumulate inthe bent portion 31 a, at which each glass bulb is bent into a U-likeshape. Such an accumulation of the glass makes the inner face of thebent portion 31 a prone to cracks. By limiting the bulb wall thicknesswithin the range from 0.7 to 1.0 mm, however, the embodiment is capableof reducing the danger of glass accumulating inside each bent portion 31a.

The maximum width of the circuit board 24 is so set as to range up to1.2 times the maximum dimension along which the U-shaped bent bulbs 31of the arc tube 18 are arranged, and the electrical components 26 thathave relatively high heat resistance are mounted on one side of thecircuit board 24, i.e. the side facing the arc tube 18, while theelectrical components 25 having relatively low heat resistance aremounted on the other side of the circuit board 24. Thus, the embodimentis capable of reducing the size of the circuit board 24 while limitingthe influence that heat exerts on the electrical components 25, 26mounted on the circuit board 24. Consequently, the embodiment is capableof reducing the dimensions of the cover 14, which contains the circuitboard 24 to a level equivalent to the dimensions of a typical lightbulb. The influence that the heat from the electrodes exerts on theelectrical components 26 can be limited by positioning the electricalcomponents 26 apart from the electrodes of the arc tube 18 when theelectrical components 26 are mounted on the side of the circuit board 24facing the arc tube 18. Although it is recommended that the circuitboard 24 have a circular shape, which is the most effective shape toensure the space for mounting, the circuit board 24 may have a polygonalshape, such as a square, or an oval shape.

The arc tube 18 comprises three or more U-shaped bent bulbs 31, each ofwhich has a smoothly bent crown P. These U-shaped bent bulbs 31 areserially connected to one another and concentrically arranged in such amanner that their crowns P are aligned in a circle and face the innersurface of the globe 17 and that the U-shaped bent bulbs 31 are spacedapart at a distance not exceeding the outer diameter of each bulb. Thus,this configuration makes it possible to dispose the arc tube 18 in theglobe 17 that is formed in a compact shape resembling a typical lightbulb. This embodiment is also capable of providing more uniformluminosity and more effective illumination even if the arc tube 18 iscontained in such a compact globe 17.

As the arc tube 18 can be produced simply by forming three U-shaped bentbulbs 31 having an essentially identical shape and connecting themtogether, without the need of bending a glass tube into a complicatedshape, the present embodiment is capable of reducing the productioncosts.

According to the configuration of the embodiment, the globe 17 includesan arc tube 18 comprised of a plurality of U-shaped bent bulbs 31 havingan outer bulb diameter ranging from 8 to 11 mm and arranged parallel toone another in such a manner that the maximum width of the arc tube 18,i.e. the dimension along which the U-shaped bent bulbs 31 are arrangedranges from 32 to 43 mm. Furthermore, the maximum outer diameter of theglobe 17 is in the range from 55 to 60 mm, and the globe 17 encloses thearc tube 18 in such a manner that A2>A1≧A3, wherein A1 represents theminimum distance between the globe 17 and each crown P of the arc tube18; A2 represents the minimum distance between the maximum diameterportion of the globe 17 and the arc tube 18; and A3 represents theminimum distance between the base end of the globe 17 and the arc tube18. Therefore, the embodiment is capable of determining the optimumcriteria for luminance intensity distributing in the directions of thesides and the front end of the arc tube 18. Based on the aboveinequality, the optimum criteria for luminance intensity distributing inthe directions of the sides and the front end of the arc tube 18 can beprovided by setting A1 in the range from 2 to 8 mm, A2 in the range from3 to 13 mm and A3 in the range from 2 to 8 mm.

In case, for example, a self-ballasted fluorescent lamp according to thepresent embodiment is used for a ceiling-recessed type down light, alarge portion of the light is distributed toward the base. In otherwords, the characteristics of luminous intensity distribution of thelamp are similar to those of an incandescent lamp so that the reflectordisposed in the luminaire achieves the designed optical effect, with thelight effectively radiated to the reflector, which is located near thesocket. In case the lamp is used for a table lamp or a similar luminairewhich is designed to project the image of the internal light source ontoa photo-diffusing shade, which may be made of cloth, setting the lamp soas to have luminous intensity distribution characteristics similar tothose of an incandescent lamp enables the lamp to be used without anydisagreeability.

Bonding the supporting member, the arc tube and the globe to one anotherby means of a bonding agent permits the heat to be efficiently radiatedfrom the arc tube through the globe and also simplifies the structure,thereby enabling the reduction of the production costs.

Furthermore, the arc tube 18 is formed in a compact shape with itsU-shaped bent bulbs 31 arranged in such a manner that their crosssections give the appearance of a triangle.

The distance w1 between the two straight portions 31 b of each U-shapedbent bulb 31 is nearly identical to the distance w2 between eachstraight portion 31 b and the U-shaped bent bulb 31 adjacent to saidstraight portion 31 b, and the distances w1, w2 are in the range between1 mm and 5 mm. Therefore, the arc tube 18 is disposed in a compactconfiguration.

Through the control circuit 54, the lighting circuit 16 operates theN-channel field effect transistor Q1 and the P-channel field effecttransistor Q2. As the output from a single control circuit 54 thuscontrols two field effect transistor s in different conditions, theconfiguration of the circuit is simplified. By using a lighting circuit16 which, as described above, requires only a minimal number of parts,the dimensions of the self-ballasted fluorescent lamp 10 can be furtherreduced.

As a lamp according to the embodiment has an outer shape resembling atypical light bulb having a rated power of approximately 60 W, it can bemounted on a luminaire designed for a typical light bulb. Thus, theembodiment expands the range of usage and also improves the appearance,permitting the lamp to be used without giving any disagreeability.

As shown in FIG. 3, the embodiment described above calls for securingthe fitting edge 17 a of the globe 17 by injecting a bonding agent 37into the groove that is formed between the fitting step portion 35 andthe cover 14. However, these parts may be affixed by using variousmeans.

For example, a groove open at the bottom may be formed along the outercircumferential edge of the partition plate 33 that secures the arc tube18 so that the globe 17 may be secured by fitting the fitting edge 17 aof the globe 17 in this groove and injecting a bonding agent 37, such asa silicon-based bonding agent, into the groove. In an alternativeconfiguration, the cover 14 and the partition plate 33 may respectivelybe provided with a catching portion and a catching portion receiver sothat the cover 14 and the partition plate 33 can be secured by engagingthe catching portion of the cover 14 and the catching portion receiverof the partition plate 33 with each other. This engagement of thepartition plate 33 and the cover 14 can be done by inserting thepartition plate 33 into the cover 14, or inserting the partition plate33 into the cover 14 and then rotating the partition plate 33 in a givendirection. According to this configuration, wherein the globe 17 isfastened only to the partition plate 33, the members forming the arctube 18 and the components of the lighting circuit 16 can be separatedand recovered more easily compared with the configuration which callsfor attaching the arc tube 18 and the lighting circuit 16 to thepartition plate 33 and fixing the globe 17 in the state where the cover14 is attached to the partition plate 33. The above configuration hassuch other benefits that it improves the appearance of the lamp bysimplifying the structure of the components exposed to the outside andthat it is applicable to a luminaire of other types, e.g. a luminairewhich does not use a globe 17.

As an alternative way to fix the globe 17, a notch or a groove may beformed in the partition plate 33, in the fitting step portion 35 orother location near the globe 17 and the arc tube 18, so that the cover14, the globe 17, the partition plate 33 and the arc tube 18 mayintegrally be bonded together by introducing a bonding agent 37, such asa silicon type bonding agent, into this notch or the groove, therebybonding the cover 14, the globe 17 and the partition plate 33 to oneanother. This configuration is capable of reducing the production costs,because its structure and production process are simpler than theconfiguration which calls for bonding the cover 14, the globe 17 and thepartition plate 33 together and bonding the arc tube 18 to the partitionplate 33 in a separate production process. In addition, it is capable offastening the arc tube 18 to the globe 17 more securely. Furthermore,because the above configuration permits the heat to be conducted fromthe arc tube 18 through the bonding agent 37 to the globe 17 andefficiently radiated through the globe 17, it is capable of limitingdeterioration of the luminous flux as well as increase in thetemperature of the lighting circuit 16 and, consequently, capable ofincreasing the reliability of the circuit.

Although the lighting circuit 16 according to the embodiment describedabove is disposed in such a manner that a single circuit board 24 ispositioned horizontally, in other words perpendicularly to the directionin which the base 12 is inserted, it does not matter whether a pluralityof circuit boards are provided or the circuit board(s) are positionedperpendicularly, i.e. in parallel to the direction in which the base 12is inserted.

The lighting circuit 16 may be composed by arranging a first circuitboard and a second circuit board in such a manner that both circuitboards extend horizontally one above the other. In this embodiment, theupper first circuit board has electrical components 25 mounted thereon,while electrical components 25 are-mounted on the underside of thesecond circuit board located at the lower side, and the first and secondcircuit boards are arranged with their soldered sides facing each other.The electrical components 25 consisting of components having relativelylow heat resistance, such as electrolytic condensers or film condensers,are mounted on the first circuit board disposed at the side where thebase 12 is located, while electrical components 25, a large part ofwhich consists of those having relatively high heat resistance andhaving little thickness, such as resistors or chip components forrectification, are mounted on the second circuit board. The first andsecond circuit boards are electrically connected via a plurality ofjumper wires, which may be two or three tinned wires, or flexible,film-like cables. When the first circuit board and the second circuitboard are incorporated in the lamp, the mounting of these circuit boardsis done by bending the jumper lines in such a manner that the solderedsides of these two circuit boards face each other. Disposed between thesoldered sides of the first and second circuit boards is an insulatingsheet which is approximately 1 mm thick and made of an insulating,heat-resistant material having an excellent heat insulating capability,such as a silicon-type film or the like. Thus, the soldered sides areinsulated from each other, and conduction of heat from the arc tube 18to the first circuit board is limited. By dividing the circuitcomponents into two circuit boards, the planar dimensions of thelighting circuit 16 is reduced. By thus making the circuit mountingstructure compact, the above configuration provides a lamp having ashape nearly identical to that of a typical light bulb. Dividing thecircuit components into two circuit boards has such other benefits as toenable the easy protection of electrical components 25 having low heatresistance and improve the reliability and facilitates mass-productionof the lamp.

In the configuration described above, components having low heatresistance, such as film condensers, and ballast chokes that generate agreat amount of heat may undergo what is generally called ‘siliconpotting’, i.e. a treatment which calls for placing silicon-based bondingagent on these components. Or a silicon-based resin rubber may bedisposed in the space provided between the second circuit board and thepartition plate 33 and filled with air. As thus using silicon potting orresin rubber enhances the outgoing radiation of heat from the electricalcomponents 25 and makes it difficult for the heat from the arc tube 18to be conducted to the electrical components 25, the temperature of theelectrical components 25 can be reduced.

Although the configuration described above calls for sealing the ends ofthe arc tube 18 by means of line sealing using a mount, they may besealed by means of pinch sealing that does not use a mount so thatproduction costs can be reduced by excluding the process for producingmounts.

In an alternative configuration, the ends of the arc tube 18 may besealed by means of pinching that uses a jig. In case of a conventionalconfiguration, supporting the filament coils 44 is typically done byclamping each filament coil 44 with a pair of copper-weld wires 45 fixedto a bead glass (a mount bead). Therefore, depending on the position orinclination of each bead glass, pinching with a jig presents the dangerof damaging the phosphor film applied to the inner surface of the arctube 18 and consequently degrading the quality of the arc tube 18.According to the present embodiment, however, a mount used at each ofthe hot cathode fluorescent lamp permits the corresponding filament coil44 to be directly clamped by two copper-weld wires 45, and each clampingwidth is limited to 7 mm or less. By thus eliminating the need ofsophisticated control of the positions and inclinations of the beadglass, which control is essential in cases where bead glasses are used,the present embodiment simplifies the production process of the arc tube18, thereby reducing its production costs, and also improves the qualityof the arc tube 18. In case of the present embodiment, too, thecopper-weld wires 45 at one side or the other are provided with anauxiliary amalgam 49.

Conventionally, sealing by pinching is done by directly pinching thedumet wires 46 of the copper-weld wires 45 with the arc tube 18 to sealthe dumet wires 46 in the arc tube 18. As setting appropriate heatingcriteria, such as duration, temperature, etc. to securely bond the metaldumet wires 46 and the glass act tube 18 is difficult and requiressophisticated production technology, the conventional method of pinchingdescribed above not only makes the reduction of production costsdifficult but also presents a problem in that the occurrence of anyimproper sealing would degrade the quality of the arc tube 18. One ofthe solutions to such problems is welding the glass to the dumet wires46, i.e. the dumet portions, of the copper-weld wires 45 beforehand andthen attaching the dumet wires 46 to the arc tube 18 and thus sealingthem in the arc tube 18 by pinching. Doing so facilitates the sealing ofthe arc tube 18, thereby improving the quality of the arc tube 18,increasing the yield and reducing production costs. Furthermore, in theabove configuration, bead glass, each of which is adapted to support twocopper-weld wires 45, may be used.

According to the embodiment described above, a self-ballastedfluorescent lamp is provided with a globe 17 whose shape is similar tothe glass bulb of a typical light bulb having a rated power consumptionof approximately 60 W. However, the shape of the globe 17 is not limitedto the glass light bulb of a typical light bulb, and various shapes areapplicable. Furthermore, a configuration which does not have a globe 17is also applicable.

FIG. 9 is a side view of a partially-cutaway self-ballasted fluorescentlamp according to a seventh embodiment of the present invention, andFIG. 10 is a side view of a partially-cutaway self-ballasted fluorescentlamp according to an eighth embodiment of the present invention.

In the embodiment shown in FIG. 9, the arc tube 18 is exposed from thecover 14, because a globe 17 is not provided. This configurationprovides a self-ballasted fluorescent lamp which is even more compact,more suitable to be used for a luminaire that uses a typical light bulb,and improves the total luminous flux characteristic.

By forming a globe 17 in the shape of a ball, the embodiment shown inFIG. 10 is capable of providing a globe 17 whose shape resembles aball-type glass bulb of a typical light bulb.

Although each one of the embodiments described above uses a milky whiteglobe 17, a transparent globe, i.e. a clear-type globe, may be used.

A luminaire may be formed by attaching a self-ballasted fluorescent lamp10 according to any one of the embodiments described above to the mainbody of a luminaire which is provided with a socket designed for atypical light bulb for general illumination. As a result, a luminairehaving benefits described above, such as having more uniform luminance,being capable of improving the illumination efficiency and reducingproduction costs, can be provided.

According to each embodiment described above, an arc tube 18 is formedby connecting three U-shaped bent bulbs 31. However, the shape of thearc tube 18 is not limited to such a configuration; the lamp length maybe reduced by arranging a plurality of U-shaped or H-shaped bent bulbs,e.g. two, three or four bulbs, in parallel with one another so as toform a discharge path having four, six or eight axes extending in thelengthwise direction of the lamp.

Next, a self-ballasted fluorescent lamp and a luminaire according to theninth embodiment of the invention are explained hereunder, referring todrawings.

FIG. 11 is a sectional view of a part of a self-ballasted fluorescentlamp according to an embodiment of the present invention; FIG. 12 is aperspective of a part of said self-ballasted fluorescent lamp; and FIG.13 is a schematic illustration of the self-ballasted fluorescent lamp asviewed from the bottom.

The self-ballasted fluorescent lamp according to the ninth embodimenthas the same appearance as that of the lamp shown in FIG. 1.

In FIGS. 11 through 13, numeral 10 denotes a self-ballasted fluorescentlamp. The self-ballasted fluorescent lamp comprises a cover 14 having abase 12, a lighting circuit 16 contained in the cover 14, a translucentglobe 17, and an arc tube 18 contained in the globe 17. The globe 17 andthe cover 14 together form an envelope 19 that has such an outer shapeas to have nearly the same dimensions as standard dimensions of anincandescent lamp having a rated power of approximately 60 W. In otherwords, the lamp length H1 of the envelope 19 ranges from approximately120 to 125 mm including the base 12; the diameter D1 of the envelope 19,i.e. the outer diameter of the globe 17, is approximately 60 mm; and themaximum diameter D2 of the cover 14 is approximately 40 mm. Further, inthe explanation hereunder, the side where the base 12 is located isreferred to as the upper side, while the side where the globe 17 islocated is referred to as the lower side.

The cover 14 is provided with a cover body 21 that may be formed of aheat resistant synthetic resin such as polybutylene terephthalate (PBT).The cover body 21 has an approximately cylindrical shape that flaresdownward. The base 12, which may be of the E26 Edison type, is disposedover the top of the cover body 21 and fastened thereto with a bondingagent, or by such other means as crimping.

The globe 17 may be transparent or photo-diffusing milky white. Theglobe 17 is formed of glass, synthetic resin or the like into a smoothlycurved shape that is nearly identical to the glass bulb of anincandescent lamp. The edge of the opening of the globe 17 is formedinto a fitting edge 17 a to be fitted in an opening at the bottom of thecover 14. The globe 17 may be formed in combination with another member,such as a diffusion film, in order to make luminance of the lamp moreuniform, or the globe 17 may entirely be omitted.

The lighting circuit 16 contained in the cover 14 has a circuit board (aPC board) 24 disposed horizontally, in other words perpendicularly tothe lengthwise direction of the arc tube 18. A plurality of electricalcomponents 25, 26 are mounted on both sides of the circuit board 24,i.e. the upside facing the base 12 and the underside facing the arc tube18, thereby forming an inverter circuit (a high-frequency lightingcircuit) for conducting high frequency lighting.

The electrical components 25 mainly consisting of components havingrelatively low heat resistance, such as electrolytic condensers and filmcondensers, are arranged on the upside of the circuit board 24, whilethin, small chip-shaped electrical components (chip components) 26having relatively high heat resistance are arranged on the underside ofthe circuit board 24. Said chip-shaped electrical components (chipcomponents) 26 consist of rectifiers (rectifying devices or diodebridges), transistors, resistors, etc. and are arranged in a packageapproximately 2 to 3 mm in thickness. The circuit board 24 has a shaperesembling a disk having a diameter less than that of a roughly circularshape with a diameter of 40 mm. Wires drawn out of the circuit board 24are connected to the electrodes 61 of the arc tube 18.

The arc tube 18 consists of three U-shaped bent bulbs 31 that are tubeshaving nearly identical shapes and arranged at given locations. Thethree U-shaped bent bulbs 31 are connected to one another viacommunicating tubes 32 and thus form a single discharge path. Anelectrode 61 having a filament coil and other necessary parts isdisposed at each end of the discharge path. Each U-shaped bent bulb 31is provided with a phosphor film, which is formed on the inner surfaceof the U-shaped bent bulb 31, hermetically contained a rare gas, such asargon, and mercury. Each U-shaped bent bulb 31 is a glass cylindricalbulb having an outer tube diameter of 10 mm and an inner tube diameterof 8 mm. In other words, the wall thickness of each bulb is 1 mm. EachU-shaped bent bulb 31 is formed into a smoothly curved U-like shapehaving a crown P by bending said glass bulb, which is 110 mm long, atthe middle portion so that the bulb 31 has a bent portion 31 a that issmoothly turned back on itself and a pair of straight portions 31 bextending parallel to each other and integrally connected to the bentportion 31 a.

The arc tube 18 is fastened to a partition plate 33, which may bereferred to as a supporting member in the claims or other parts of thespecification and serves as a fluorescent lamp fastening member as wellas a lighting circuit fastening member. The partition plate 33 isfastened to the cover 14. To be more specific, the partition plate 33has a disk-shaped base portion 34 which is provided with mounting holes34 a. The arc tube 18 is fastened to the partition plate 33 with theends of the U-shaped bent bulbs 31 respectively inserted into themounting holes 34 a and secured therein by means of, for example,bonding the regions of the bulbs to the base portion with an adhesiveagent. A fitting step portion 35 that extends upward and then outward isformed around the outer edge of the base portion 34. These members arefastened together by fitting the fitting step portion 35 in the cover 14and filling the gap between the fitting step portion 35 and the cover 14with a bonding agent 37 in such a state that the fitting edge 17 a ofthe globe 17 is fitted between the fitting step portion 35 and the cover14. A mounting edge 38 that may have a cylindrical shape rises from thetop of the fitting step portion 35, and the circuit board 24 of thelighting circuit 16 is fitted, bonded or otherwise attached to themounting edge 38.

One of the two ends of each U-shaped bent bulb 31 is sealed by means ofline sealing with a mount, pinch sealing without a mount, or the like. Aminute tube 41 that may otherwise be called an exhaust tube is welded tothe other end of each U-shaped bent bulb 31 to discharge the air. Theminute tube 41 is designed such that it may be provided with an amalgamif it is necessary. An electrode 61 is disposed at the end of eachU-shaped bent bulb 31 that is located at an end of the discharge path ofthe arc tube 18 in such a state that the filament coil of each electrode61 is supported between a pair of copper-weld wires (lead-in wires). Viaeach respective dumet wire attached to the glass end of the U-shapedbent bulb 31 and thus sealed in the bulb, each copper-weld wire isconnected to a lamp wire that is drawn out of the U-shaped bent bulb 31.Said lamp wires are electrically connected to the lighting circuit If itis necessary, one of the copper-weld wires may be provided with anauxiliary amalgam.

In the state where the self-ballasted fluorescent lamp 10 is assembled,as shown in FIG. 13, the chip-shaped electrical components 26 mounted onthe underside of the circuit board 24 are located apart from the ends ofthe U-shaped bent bulbs 31 of the arc tube 18, particularly from theminute tubes 41 projecting from the ends of the U-shaped bent bulbs 31.The electrical components 26 are also spaced apart from the electrodes61, in other words they are positioned near the U-shaped bent bulbs 31that are not provided with an electrode 61.

When the self-ballasted fluorescent lamp 10 is assembled in the mannerdescribed above, the arc tube 18 is housed in the globe 17 at a givenposition. To be more specific, in the state where the self-ballastedfluorescent lamp 10 is assembled, the crowns P of the U-shaped bentbulbs 31 are aligned at regular intervals in a circle whose center is onthe central axis of the self-ballasted fluorescent lamp 10 extending inthe vertical direction, and the straight portions 31 b of the U-shapedbent bulbs 31, too, are aligned at regular intervals in a circle whosecenter corresponds to the central axis of the lamp. The straightportions 31 b are aligned in a circle in such a manner that the distanceW between each straight portion 31 b and its adjacent straight portion31 b is less than 10 mm, in other words shorter than the outer diameterof each U-shaped bent bulb 31.

The self-ballasted fluorescent lamp 10 structured as above has suchcharacteristics that, when a rated input power is 14 W, a high frequencypower of 12.5 W is applied to the arc tube 18, producing a lamp currentof 280 mA, a lamp voltage of 65 V and a total luminous flux of 810 lm,which results from the use of the three band phosphor.

By mounting electrical components 25, 26 on both ends the circuit board24 as described above, the present embodiment is capable of reducing thesize of the circuit board 24 and also reducing the diameter of the cover14, which is located near the base 12.

As the circuit board 24 is so formed as to have an outer diameter nearlyidentical to the inner diameter of the cover 14 and cover the interiorof the cover 14, it is possible to arrange components by making use ofthe space inside the cover 14 to the full extent and, consequently,reduce the diameter of the portion of the cover 14 near the base 12.

According to the present embodiment, the circuit board 24 and the arctube 18 are positioned one directly above the other. However, as thechip-shaped electrical components 26 mounted on the side of the circuitboard 24 facing the arc tube 18 are so positioned as to not face theends of the U-shaped bent bulbs 31 of the arc tube 18, particularly theportions of the ends of the U-shaped bent bulbs 31 from which the minutetubes 41 project, the embodiment described above is capable ofpreventing interference of the arc tube with the electrical components26, limiting the influence of the heat from the arc tube, and reducingthe length of the lamp by the thickness of the chip-shaped electricalcomponents 26, i.e. 2 to 3 mm.

By disposing the electrical components 26 mounted on the side of thecircuit board 24 facing the arc tube 18 at locations removed from theelectrodes 61 of the arc tube 18, the embodiment is also capable oflimiting the influence that the heat generated by the electrodes 61exerts on the electrical components 26, thereby increasing thereliability of the electrical components.

As the arc tube 18 is formed by parallely arranging U-shaped bent bulbs31 that have a U-like shape, the length of the lamp can be reduced.

By reducing the length of the bulb as well as the diameter of theportion of the lamp near the base 12, e.g. the portion extending up to+mm from the base 12, so as to make the shape of the lamp resemble atypical PS-type electric bulb, the embodiment described above provides alamp having a shape similar to that of an incandescent lamp. Therefore,the self-ballasted fluorescent lamp 10 described above can be mounted ona luminaire designed for an incandescent lamp. Thus, the embodimentexpands the range of its usage and also improves the appearance of thelamp, permitting the lamp to be used without giving any disagreeability.

According to the embodiment described above, an arc tube 18 is formed byconnecting three U-shaped bent bulbs 31. However, the shape of the arctube 18 is not limited to such a configuration; the lamp length may bereduced by arranging a plurality of U-shaped or H-shaped tubes, e.g.two, three or four tubes, in parallel with one another so as to form adischarge path having four, six or eight axes extending in thelengthwise direction of the lamp. Furthermore, although the lightingcircuit 16 is comprised of a single circuit board 24 that is positionedhorizontally, it may consists of a plurality of circuit boards.

A luminaire may be formed by attaching a self-ballasted fluorescent lamp10 according to any one of the embodiments described above to the mainbody of a luminaire which is provided with a socket designed for anincandescent lamp or the like. Thus formed luminaire has the variousbenefits of the self-ballasted fluorescent lamp 10 described above.

Every configuration described above is applicable to a bent-tube typefluorescent lamp, which may be installed in a luminaire using aball-shaped fluorescent lamp or the like.

Next, a fluorescent lamp according to yet another embodiment of theinvention is explained hereunder, referring to drawings.

The tenth embodiment is shown in FIGS. 14 through 17, wherein FIG. 14(a) is an exploded view of a bulb of the fluorescent lamp; FIG. 14( b) isan enlarged sectional view of the part A in FIG. 14( a); FIG. 15 is aside view of said fluorescent lamp; FIG. 16 is a top view of same,wherein the globe of said fluorescent lamp is illustrated as if theinside contents were visible; and FIG. 17 is a sectional view of a partof said fluorescent lamp.

In the drawings, numeral 111 denotes a fluorescent lamp having a shapeof a light bulb (hereinafter called self-ballasted fluorescent lamp).The self-ballasted fluorescent lamp 111 comprises a cover 113 having anE26-type base 112, a lighting circuit (not shown) contained in the cover113, a translucent globe 114, and an arc tube 115 contained in the globe114. The cover 113 and the globe 114 together form an envelope 19 thathas such an outer shape as to have nearly the same dimensions asstandard dimensions of a typical light bulb for general illumination. Inother words, the height of the envelope ranges from approximately 110 to125 mm including the height of the base 112, while the diameter of theenvelope, i.e. the outer diameter of the globe 114, ranges fromapproximately 55 to 60 mm Further, in the explanation hereunder, theside where the base 112 is located is referred to as the lower side,while the side where the globe 114 is located is referred to as theupper side.

The cover 113 is provided with a cover body 121 that may be formed of aheat resistant synthetic resin such as polybutylene terephthalate (PBT).The cover body 121 has an approximately cylindrical shape that flaresupward. The base 112, which may be of the E26 type, is disposed over thebottom of the cover body 121 and fastened thereto by way of bonding,crimping or any other appropriate means.

The globe 114 may be transparent or photo-diffusing milky white. Theglobe 114 is formed of glass, synthetic resin or the like into asmoothly curved shape nearly identical to the glass bulb of a lightbulb, with the edge of its opening fitted in an opening at the top ofthe cover 113 and fastened thereto. The luminance of the lamp may bemade more uniform by forming the globe 114 in combination with anothermember, such as a diffusion film.

A combination of such a globe 114 as described above and a bulb 131,which will be described later, increases the output power of the lightirradiated in the direction of the base 112 and thereby achievesluminous intensity distribution whose characteristics are similar tothose of a light bulb for general illumination.

The lighting circuit is comprised of an inverter circuit (ahigh-frequency lighting circuit) for lighting the arc tube 115 at a highfrequency. The lighting circuit consists of an approximately disk-shapedboard on which electronic components are mounted. The maximum outerdiameter of the lighting circuit is 40 mm.

The arc tube 115 has a bulb 131. A film of phosphor 132 is formed on theinner surface of the bulb 131; The bulb 131 hermetically contains fillergas which is a rare gas, such as argon, and mercury. The bulb 131 alsocontains a pair of electrodes 133, which are respectively disposed atthe two ends of the bulb 131.

The bulb 131 has three tubular bodies 134 a, 134 b, 134 c, each of whichmay be an approximately cylindrical glass tube having an outer tubediameter ranging from 8 to 11 mm and an inner tube diameter ranging from6 to 9 mm and a wall thickness ranging from 0.7 to 1.0 mm, and formedinto a smoothly curved U-like shape having a crown 135 by bending saidglass tube at the middle of its length, which ranges from approximately110 to 130 mm. Therefore, each tubular body 134 a, 134 b, 134 c has abent portion 136 that is smoothly turned back on itself and a pair ofstraight portions 137 extending parallel to each other and integrallyconnected to the respective two ends of the bent portion 136.

The two ends of the tubular body 134 b, which is located at the middlepart of the bulb 131, are respectively connected through communicatingtubes 138 to one end of the tubular body 134 a and one end of thetubular body 134 c, which are respectively located at the ends of thebulb 131, so that a single continuous discharge path 139 having a lengthranging from 200 to 300 mm is formed. In the state where the bulb 131 isincorporated in the self-ballasted fluorescent lamp 111, the crowns 135(the bent portions 136) of the tubular bodies 134 a, 134 b, 134 c arealigned at regular intervals in a circle whose center is on the centralaxis of the self-ballasted fluorescent lamp 111 extending in thevertical direction, and the straight portions 137 of the tubular bodies134 a, 134 b, 134 c, too, are aligned at regular intervals in a circlewhose center corresponds to the central axis of the lamp. To be morespecific, the straight portions 137 of each tubular body 134 a, 134 b,134 c are arranged along each respective side of a triangle that forms across section of the bulb 131. The straight portions 137 aligned in acircle are formed so that the distance between each straight portion 137and its adjacent straight portion 137 is shorter than the outer diameterof each tubular body 134 a, 134 b, 134 c.

The tubular bodies 134 a, 134 b, 134 c are respectively provided withcylindrical minute tubes 140 a, 140 b, 140 c that may otherwise becalled exhaust tubes. Each minute tube 140 a, 140 b, 140 c communicateswith the corresponding tubular body 134 a, 134 b, 134 c and projectsfrom an end thereof. However, each one of the minute tubes 140 a, 140 cof the tubular bodies 134 a, 134 c, which are respectively located atthe two ends of the bulb 131 projects from the non-electrode end, i.e.the end opposite the end at which an electrode 133 is attached. The airis discharged from the bulb 131 through the minute tubes 140 a, 140 b,140 c or a part of these minute tubes 140 a, 140 b, 140 c, while thefiller gas is introduced. After the filler gas has replaced the air, thebulb 131 is sealed by fusing the minute tubes 140 a, 140 b, 140 c. FIG.14 schematically illustrates the state of the minute tubes 140 a, 140 b,140 c prior to fusion. Each minute tube 140 a, 140 b, 140 c has an openend portion 141 that communicates with the corresponding tubular body134 a, 134 b, 134 c. The inner diameter 12 of each open end portion 141is smaller than the inner diameter L1 of the barrel portion of eachminute tube 140 a, 140 b, 140 c.

Of the minute tubes 140 a, 140 b, 140 c of the tubular bodies 134 a, 134b, 134 c, the minute tube 140 a (or the minute tube 140 c), which islocated closest to either electrode 133 hermetically contains an amalgam142. Said minute tube 140 a (or the minute tube 140 c) is located at thenon-electrode end of the tubular body 134 a (or the tubular body 134 c)at either end of the bulb 131, non-electrode end meaning the endopposite the end at which the electrode 133 is enclosed. The amalgam 142is enclosed in the minute tube 140 a (or the 140 c), when the minutetube is sealed. The amalgam 142 is an alloy of bismuth, indium andmercury formed into a nearly spherical shape whose diameter is greaterthan that of the open end portion 141 of the minute tube 140 a and hasthe function of controlling the pressure of the mercury vapor in thebulb 131 within an appropriate range. The amalgam 142 may be formed ofan alloy that consists of tin and lead in addition to bismuth andindium.

If it is necessary, an auxiliary amalgam may be disposed in the bulb 131so as to absorb mercury floating in the bulb when the lamp is turnedoff, and release the absorbed mercury during the early stage oflighting, including the moment when the lighting is initiated.

Each electrode 133 has a filament coil 143 supported by a pair ofcopper-weld wires (lead-in wires) 145, each of which is fixed by a beadstem 144. Via a dumet wire 146 attached to the glass of the end of thecorresponding tubular body 134 a, 134 c and thus sealed in the tubularbody, each copper-weld wire 145 is connected to a wire 147 that is drawnout of each respective tubular body 134 a, 134 c. Each dumet wire 146 isenclosed in the bulb by means of a pinch seal portion 148 provided atthe end of the bulb. When the bulb 131 is installed in a self-ballastedfluorescent lamp 111, the wires 147 are connected to the lightingcircuit.

FIG. 17 illustrates the relationships that the inner diameter b of eachcommunicating tube 138 and the width c of each electrode 133 have withrespect to the inner tube diameter a of the bulb 131. The communicatingtubes 138 are formed by joining the apertures of the tubular bodies toone another. Said apertures are formed prior to the sealing of theminute tubes 140 a, 140 b, 140 c, by heating and melting the tubularbodies and then breaking through the appropriate portions by blowing airthrough the tube walls.

The relationship between the inner tube diameter a of the bulb 131 andthe inner diameter b of each communicating tube 138 is set such that0.6<a/b<1.0 in order to reduce the lamp starting voltage and improve therise of the light output.

The relationship between the inner tube diameter a of the bulb 131 andthe width c of each electrode 133 is set such that (a−c)/2<1.5 mm sothat the electrodes 133 generate excessive heat when the lamp reachesthe last stage of its life and that the generated beat melts the bulb131 and causes the filler gas to leak from the bulb, thereby turning offthe lamp to become unilluminated.

The self-ballasted fluorescent lamp 111 structured as above hascharacteristics such that, when a rated input power is 14 W, a highfrequency power of 12.5 W is applied to the arc tube 18, producing alamp current of 280 mA, a lamp voltage of 65 V and a total luminous fluxof 810 lm, which results from the use of the three band phosphor.

Next, the function of the embodiment described above is explained.

By enclosing the amalgam 142 in the minute tube 140 a, which is the one,among the minutes tubes 140 a, 140 b, 140 c located at the middleportion of the bulb 131, closest to one of the electrodes 133, it ispossible to prevent the temperature of the amalgam 142 from becoming toohigh due to the influence of the heat from the electrode 133 and alsofacilitate the warming of the amalgam 142 at the initiation of lighting.

In other words, compared with the configuration where an amalgam 142 isdisposed at the end of the bulb 131 at which an electrode 133 isattached, the above configuration according to the present embodiment iscapable of reducing the influence that heat from an electrode 133 exertson the amalgam 142, thereby preventing the temperature of the amalgam142 from becoming too high, and also capable of limiting the pressure ofthe mercury vapor within an appropriate range. In addition, by reducingthe distances from the amalgam 142 to the two respective ends of thebulb 131, the above configuration is capable of making the pressure ofthe mercury vapor in the entire bulb 131 uniform and stable.Furthermore, compared with the configuration where an amalgam 142 isdisposed in the tubular body 134 b at the middle portion of thebulb-131, the present embodiment permits the amalgam 142 to be heatedeasily. Therefore, the embodiment is capable of improving the risingcharacteristics of the luminous flux and consequently reducing the timetaken for the luminous flux to become stable.

As described above, by enclosing the amalgam 142 in the minute tube 140a (or minute tube 140 c), which is the one, among the minutes tubes 140a, 140 b, 140 c located at the middle portion of the bulb 131, closestto one of the electrodes 133, the embodiment is capable of preventing anunfavorable influence of the heat from the electrode 133 from increasingthe temperature of the amalgam 142 too much and also facilitating thewarming of the amalgam 142 at the initiation of lighting. As a result,it is possible to limit the pressure of the mercury vapor within anappropriate range and reduce the time taken for the luminous flux tobecome stable when lighting is initiated.

By enclosing the amalgam 142 in the minute tube 140 a located at thenon-electrode end of the tubular body 134 a that is located at an end ofthe bulb 131, the embodiment is capable of maintaining the pressure ofthe mercury vapor within an appropriate range and reducing the timetaken for the luminous flux to become stable when lighting is initiated.

As the inside of the minute tube 140 a, in which the amalgam 142 iscontained, is wider than the open end portion 141 that communicates withthe inside of the tubular body 134 a, the amalgam 142 can snugly becontained in the minute tube 140 a.

In cases where the inside of the bulb 131 is narrow, in other wordswhere the inner tube diameter of the bulb 131 ranges from 6 to 9 mm, itis difficult to form minute tubes 140 a, 140 c, together with theelectrodes 133, at the ends (the ends where the electrodes 133 areformed) of the tubular bodies 134 a, 134 c, which are respectivelylocated at the two ends of the bulb 131. On the other hand, the minutetubes 140 a, 140 c can easily be formed at the non-electrode ends of thetubular bodies 134 a, 134 c located at the two ends of the bulb 131.Forming the minute tubes 140 a, 140 c at the non-electrode ends alsoeliminates the need of excessively reducing the diameter of the minutetubes 140 a, 140 b, 140 c even if the bulb 131 is narrow with its innertube diameter ranging from 6 to 9 mm.

As the three tubular bodies 134 a, 134 b, 134 c are arranged in such amanner as to respectively correspond to the sides of a triangle thatforms a cross section of the bulb 131, the bulb 131 can be made into acompact shape without the need of being bent into a complicated shape,such as one resembling a saddle. A compact bulb 131 formed in the manneras described above can be used for a self-ballasted fluorescent lamp111.

In cases where the bulb 131 is narrow with its inner tube diameterranging from 6 to 9 mm, there arise such problems that the secondaryvoltage on the lighting circuit becomes too high, making it necessary toincrease the lamp initiating voltage and also slowing the rise of lightoutput, and that, when the lamp reaches the last stage of its life, theelectrodes 133 generate heat and exert a thermal influence on the coverbody 121 that supports the bulb 131. These problems can be solved bysetting the relationship between the inner tube diameter a of the bulb131 and the inner diameter b of each communicating tube 138 such that0.6<a/b<1.0 and the relationship between the inner tube diameter a ofthe bulb 131 and the width c of each electrode 133 such that (a−c)/2<1.5mm.

By thus setting the relationship between the inner tube diameter a ofthe bulb 131 and the inner diameter b of each communicating tube 138such that 0.6<a/b<1.0 so that the inner diameter b of each communicatingtube 138 exceeds the inner tube diameter a of the bulb 131, theembodiment is capable of reducing the lamp starting voltage andimproving the rise of the light output. The relationship between theinner tube diameter a of the bulb 131 and the width c of each electrode133 is set such that (a−c)/2<1.5 mm in order to bring the inner surfaceof the bulb 131 and each electrode 133 in close proximity to each other.Therefore, when the lamp reaches the last stage of its life, heatgenerated by the electrodes 133 causes a leak in the bulb 131 and stopsthe lighting circuit, thereby causing the arc tube to becomeunilluminated.

A luminaire may be formed by attaching a self-ballasted fluorescent lamp111 according to the embodiment described above to the main body of aluminaire which is provided with a socket designed for a typical lightbulb.

If it is necessary, the embodiment may include an auxiliary amalgam,which serves to improve the rising characteristics of luminous flux byreleasing mercury at the initial stage of lighting The 11th embodimentis shown in FIGS. 18 and 19, wherein FIG. 18 is an exploded view of thebulb of a fluorescent lamp, and FIG. 19 is a circuit diagram of alighting circuit of the fluorescent lamp.

An electrode is disposed at each end of the bulb 131 and hermeticallyenclosed in the bulb of an arc tube 115. Of the two electrodes, one isreferred to as the preheating-side electrode 133 a, while the other isreferred to as the non-preheating-side electrode 133 b. The arc tube 115including these electrodes 133 a, 133 b is adapted to cope with alighting circuit designed to light the lamp by preheating only one ofthe electrodes, i.e. the preheating-side electrode 133 a, by means of alighting device 151 connected to a power supply E. The lighting device151 may be an inverter or the like.

The tubular bodies 134 a, 134 b, 134 c of the bulb 131 are respectivelyprovided with cylindrical minute tubes 140 a, 140 b, 140 c, each ofwhich communicates with the corresponding tubular body 134 a, 134 b, 134c and projects from an end thereof. Of these minute tubes, the minutetubes 140 a, 140 c of the tubular bodies 134 a, 134 c, which arerespectively located at the two ends of the bulb 131, project from thenon-electrode ends, i.e. the ends opposite the ends at which theelectrodes 133 a, 133 b are attached.

If it is necessary, the minute tube that is closest to thepreheating-side electrode 133 a, i.e. the minute tube 140 a, may containa main amalgam 142 a, which serves as the amalgam referred to in theclaims and other parts of this specification and has the sameconfiguration as that of the amalgam 142 described above.

The pair of copper-weld wires 145 of each electrode 133 a, 133 b isprovided with an auxiliary amalgam 152 a, which is enclosed in the bulb131 together with the corresponding electrode 133 a, 133 b. Eachauxiliary amalgam 152 a consists of a foil of such a metal as stainlesssteel or a nickel, or a metal having a high melting point, such asmolybdenum, tantalum or niobium, and indium bonded to the surface ofsaid metal foil by means of plating or vapor deposition.

An auxiliary amalgam 152 b is disposed at an end of the tubular body 134that is located at the middle portion of the bulb 131. The end where theauxiliary amalgam 152 b is disposed is located opposite the minute tube140 b and at a long distance from the main amalgam 142 a. The auxiliaryamalgam 152 b has mercury vapor pressure characteristics similar tothose of the auxiliary amalgams 152 a; it absorbs mercury vapor when thelamp is turned off and releases mercury vapor when the lamp is turnedon.

With the configuration as above, by enclosing the main amalgam 142 a inthe minute tube 140 a, which is the closest minute tube to thepreheating-side electrode 133 a and is located at the non-electrode endof the tubular body 134 a at one end of the bulb 131, the embodimentmakes the main amalgam 142 easy to be warmed by the heat from thepreheating-side electrode 133 a at the initiation of lighting andimproves the rising characteristics of luminous flux.

By means of the auxiliary amalgams 152 a disposed at the electrodes 133a, 133 b and the auxiliary amalgam 152 b disposed halfway between theelectrodes 133 a, 133 b, the embodiment is capable of releasing themercury at the initial stage of lighting, thereby improving the risingcharacteristics of luminous flux.

As the auxiliary amalgam 152 b having mercury vapor pressurecharacteristics similar to those of the main amalgam 142 a and theauxiliary amalgams 152 a is enclosed in the bulb 131, the auxiliaryamalgam 152 b works in conjunction with the main amalgam 142 a and theauxiliary amalgams 152 a to maintain the pressure of the mercury vaporin the bulb 131 within an appropriate range and reduce the time takenfor the luminous flux to become stable when lighting is initiated.

Next, the 12th embodiment of the invention is shown in FIG. 20, which isa top view of a fluorescent lamp, with the globe of said fluorescentlamp illustrated as if the inside contents were visible.

A bulb 131 having a curved discharge path 139 is formed by connecting aplurality of U-shaped tubular bodies 134 a, 134 b, 134 c in such amanner that the planes defined by these tubular bodies 134 a, 134 b, 134c face one another and extend in parallel.

As the distance L3 between the electrode 133 of each tubular body 134 a,134 c and the other end of the tubular body 134 a, 134 c, i.e. the endat which the electrode is not provided, is greater than the distance L4between the electrode 133 and the corresponding end of the tubular body134 b adjacent to the electrode 133, disposing an amalgam 142 (or a mainamalgam 142 a) in the crown of the tubular body 134 b adjacent to theelectrode 133 is more effective to improve vaporization of the mercury.

In any one of the embodiments described above, the bulb may be formed byconnecting four, five or more tubular bodies.

INDUSTRIAL APPLICABILITY

As described above, a fluorescent lamp, a self-ballasted fluorescentlamp and a luminaire according to the present invention are suitable fora compact structure, in particular, a structure which uses a fluorescentlamp in place of a typical light bulb.

1. A self-ballasted fluorescent lamp comprising: an arc tube formed byparallely arranging a plurality of U-shaped bent bulbs in such a mannerthat the maximum width of the bulbs ranges from about 32 mm to about 42mm, each of which has a bent portion and straight portions; a distancew1 between the two straight portions of each U-shaped bent bulb being soset as to be nearly identical to a distance w2 between each straightportion of each U-shaped bent bulb that is adjacent to said straightportion; said distances w1, w2 being respectively limited in the rangefrom about 1 mm to about 5 mm; a cover including a base that is adaptedto permit said arc tube to be attached thereto; a lighting circuit whichincludes a circuit board having the maximum width ranging up to 1.2times the maximum width of the arc tube, said maximum width of the arctube being the dimension along which the U-shaped bent bulbs arearranged; and said lighting circuit contained in the cover in such amanner that the circuit board is positioned with one of its sides facingall the ends of the straight portions of the arc tube.
 2. Aself-ballasted fluorescent lamp, as in claim 1, wherein the U-shapedbent bulbs have an outer tube diameter ranging from about 8 mm to about11 mm.
 3. A self-ballasted fluorescent lamp, as in claim 1, wherein theU-shaped bent bulbs of the arc tube are arranged in such a manner thatthe cross sections of the U-shaped bent bulbs give the appearance of atriangle.
 4. A self-ballasted fluorescent lamp, as in claim 1, wherein:said lighting circuit includes a half-bridge type inverter main circuithaving at least a pair of transistors consisting of an N-channeltransistor and a P-channel transistor, which are connected in serieswith each other to an input power supply and serve as the main switchingelement for generating a high frequency voltage; said lighting circuitfurther includes a ballast choke connected to the main inverter maincircuit so as to light the arc tube in stable conditions; and; saidlighting circuit further includes a control means which has a secondarywinding magnetically connected to the ballast choke and shared by theN-channel transistor and the P-channel transistor so that the controlmeans serves to control the transistors by means of the secondarywinding.
 5. A luminaire including a self-ballasted fluorescent lamp asin claim 1.